23 February 2023

Global agriculture must reduce its dependence on phosphorus


Half of the available phosphorus in the soil comes from mineral fertilizers. Europe, Asia and North America show the highest concentrations. French researchers, “We need to accelerate the agroecological transition in rich countries by allocating the remaining resources to the global South”

by Matteo Cavallito


Global agricultural systems are “are extremely dependent on mineral phosphorus fertilisers.” That is, from compounds produced “from rock phosphate, a non-renewable resource that is patchily distributed across the Earth.” This imbalance therefore highlights “the importance of accelerating the agroecological transition in the Global North,” by allocating the remaining resources to the Global South and particularly to African nations characterized by less fertile soils. This is supported by a study by INRAE, the Institut national de la recherche agronomique, a French government agency, and Bordeaux Sciences Agro, a training school at the local university.

The authors, in particular, developed a model to simulate trends in available phosphorus in soils around the world from the middle of the last century to the present. The calculations are based on processing data on stocks of the element, crop yields, mineral fertilizer use, livestock numbers and international trade.

Half of the phosphorus in the soil comes from fertilizers

Globally, about 47 percent of the phosphorus in the soil is of human origin, that means it can be attributed to the use of mineral fertilizers. “This result reflects the intensification of agricultural systems that has taken place worldwide. Indeed, many countries have relied heavily on synthetic fertilisers since the 1950s.,” the authors explain.

Since then, the share resulting from the use of chemicals in agriculture in the total amount of phosphorus in the soil has increased significantly. In 2017, the latest year for which complete information is available, the figure exceeded 60 percent in Western Europe and North America.

Worldwide, however, the distribution remains highly uneven. Since the 1970s, measured concentrations in Europe have stabilized, thanks to a decrease in the use of mineral fertilizers while livestock effluents have helped to partially meet phosphorus needs. In the same decade, Asia began to experience growth in the phenomenon, later catching up with and surpassing the West. South America and Eastern Europe now have lower concentrations of about 40 percent. Finally, in Africa and Oceania, the share of phosphorus coming from fertilizers is less than 30 percent.

Distribuzione del fosforo derivante dai fertilizzanti nel suolo agricolo globale. Fonte: INRAE, 2023

Distribution of fertilizer-derived phosphorus in global agricultural soil. Source: INRAE, 2023

The phosphorus’ peak in 2050

The numbers appear somewhat paradoxical when considering that 70 percent of natural phosphate is found in just one African nation, Morocco. Europe, by contrast, is substantially devoid of it. Against this backdrop, current agricultural models end up creating great stress on the market and production, generating the conditions for new problems in the future.

“At current rates of extraction,” the researchers explain, “we will likely reach peak phosphorus (the point of maximum resource production) by 2050. Such will probably lead to an increase in fertiliser prices and greater geopolitical tensions.”

Today, many countries around the world are overly dependent on phosphorus-based mineral fertilizers and are being called upon to take new paths to overcome this situation. Among the strategies suggested by researchers are improved resource recycling and the use of mixed cropping systems that combine crops and livestock. Such a mix is capable of delivering important benefits.

Alternative solutions to protect the environment

The processing of natural phosphate, the research states, produces significant pollution through mining and processing activities. The use of alternative solutions, consequently, is not only a way to respond to problems of cost and availability of the resource. But also a genuine environmental protection strategy.

In countries that have historically relied more heavily on phosphorus, reducing fertilizer use should not necessarily impact yields, “because crops can draw upon stocks of soil-available phosphorus, depending on soil type.”

The use of rotations and the use of certain crops in particular – such as white lupin or buckwheat, for example – can promote the release of phosphorus into the soil and increase its availability for following crops. Improving the recycling of organic matter, including livestock manure and sewage plant sludge, at the same time, also contributes to the maintenance of fertility.